Apparatus for preparing blood films for the making of differential counts



D. J. B. LUBIN APPARATUS FOR PREPARING BLOOD FILMS FOR THE MAKING OF DIFFERENTIAL COUNTS Filed April 24, 1935 INVENTOR.

ATTORNEY,

Patented Feb. 4, 1936 UNITED STATES PATENT OFFICE FOR THE MAKING OF COUNTS DIFFERENTIAL David J. B. Lubin, San Francisco, Calif.

Application April 24,

4 Claims.

This invention relates to an apparatus for preparing blood films on glass slides or coverslips for the purpose of studying the individual blood cells, and more particularly, for making difierential counts.

There are two distinct methods of preparing blood films on glass slides or cover-slips for the purpose of studying individual blood cells, and more particularly, for making differential counts.

The first method is the least difficult but is the most inaccurate. In this method a drop of blood is placed on a slide, usually at one end thereof, and it is then spread out into a thin film by pushing it along with the end or edge of another slide, or with a cover-slip, or with a piece of celluloid. With this method the blood is spread out evenly but because some of the white blood corpuscles are heavier than others, they are pushed out to the edges of the film, thus making a very untrustworthy and poor distribution, which, of course, makes accurate diiierential counting impossible.

The second method is more diflicult but it gives the most accurate distribution of white blood cells so that difierential counting may be carried on with a remarkable degree of accuracy. This method consists in holding one coverslip in one hand, placing a small drop of blood in the center of it, and then dropping or laying another cover-slip over the drop of blood. When the blood has been spread out into a film by the weight of the top cover-slip, the top coverslip is pulled off in a plane parallel to the bottom slip and a blood film is formed on both coverslips.

There are several difliculties encountered when making blood films by the second method or what is known as the two cover-slip method.

First.Difiiculty in handling the thin coverslips. They break easily and are bent or buckled if too much pressure is exerted in holding them;

Second.Difiiculty in pulling the top slide off the bottom slide while maintaining it in the same plane as the bottom slide is encountered;

1935, Serial No. 17,989

tus whereby uniform pressure between the cover slips is insured; breakage and bending of thecover-slips is prevented; parallelism between the: contacting surfaces of the cover-slips is maintained; and, further, to provide an apparatus" in which the cover-slips can be readily inserted and secured and quickly released and removed when the blood films have been made.

A form of apparatus suitable for the preparation of films of blood is shown by way of illustration in the accompanying drawing, in which Fig. 1 is a perspective view of the apparatus; showing one position of the cover slips;

Fig. 2 is a similar perspective view of the apparatus showing a second position of the cover slips;

Fig. 3 is an enlarged vertical longitudinal central section of Fig. 1; and

Fig. 4 is a cross section on line IV-IV of Fig. 3.

Referring to the drawing in detail, A indicates a rectangular-shaped base member constructed of wood, bakelite, or any other suitable material. Formed in the upper surface of the base and extending substantially from end to end thereof is a dovetail slot 2 and movable longitudinally thereof is a sliding block B, having a tongue 3 extending into the slot to be guided thereby. Stop members 4 and 5 are disposed at opposite ends of the slot and prevent removal of the sliding block and also limit longitudinal move- 5' ment. I

Carried by the sliding block is a pair of spring clamping arms 6. These arms are pivoted to the block and are secured against removal by a plate I, screwed, riveted, or otherwise fastened to the block. The center portions of the arms are bent inwardly or toward each other, as shown at 8, and are then spread apart and bent downwardly, as indicated at 9, to straddle the opposite sides of the block. The spring arms are employed for the purpose of receiving and securing a cover-slip such as indicated at Hi, this slip being placed in position between the spring arms by merely inserting one of the fingers between the inwardly bent or contracted portions 8 of the arms to spread them apart, and then inserting the cover slip between the outer downwardly bent portions 9 which will grip and clamp the opposite sides of the slip the moment the finger spreading the arms apart is removed. The cover-slip, when placed between the arms, will rest upon the flat upper surface of the sliding block and will be held by it. After insertion of the slip the sliding block is moved to the position shown in Fig. 1 and the blood sample is placed thereon and on top of this is placed a second cover-slip, such as shown at H. The first cover-slip is placed between the spring arms with its sides parallel to the sides of the sliding block, while the second cover-slip, when placed on top thereof, is positioned with its sides on an approximate angle of 45 with relation to the sides of the sliding block and it is held in this position by a pair of pins |2l2 secured in the base on opposite sides of the sliding block. These pins are, in the present instance, connected at their upper ends by a cross member I 4. This member serves the function of maintaining the spacing between the pins and to a certain degree prevents bending of the same.

With the cover-slips positioned, as shown in Fig. 1, and with the blood sample placed between the same, the only operation necessary to obtain the blood film is that of sliding the block from the position shown in Fig. 1 to that shown in Fig. 2. During this movement the upper cover-slip II will be held stationary by the pins l2-l2, while the lower cover slip ID will move in unison with the block from in under the same. During this movement a film is formed on the adjacent faces of the respective cover slips and two films will be obtained. To prevent smearing of the film formed on the lower surface of the cover-slip i l, a pair of raised surfaces are provided. These may be formed by driving elongated staples into the sliding block, or in any other desired manner. Suffice it to say, that as the sliding block is moved from the position shown in Fig. l to that shown in Fig. 2, the stationary cover-slip H is transferred from its position of rest on top of the cover-slip ID to a position of rest on top of the raised members l5. It is for this reason that smudging of the film is prevented.

After the films are formed each cover-slip may be removed and dried in the usual manner. The results obtained by the use of an apparatus of this character are exceedingly uniform as absolute parallelism between the contacting faces of the cover-slips is maintained at all times. Uniform pressure is also insured and bending or breaking of the cover-slips is prevented. Furthermore, the apparatus makes available a means of making blood films by means of the two cover-slip method, both to amateurs and experts, and the result obtained is more perfect than can be obtained by the most expert hand operation; the final result being the preparation and production of a blood film whereby differential counting may be carried on with a remarkable degree of accuracy.

While certain features of the present invention are more or less specifically described, I wish it understood that various changes may be resorted to within the scope of the appended claims. Similarly, that the materials and finish of the several parts employed may be such as the manufacturer may decide, or varying conditions or uses may demand.

Havingthus described my invention, what I 1. In an apparatus for preparing a film of blood between a pair of cover-slips, a base member, a block mounted on the base and longitudinally movable thereon, means on the block for receiving and securing one of the cover-slips, said second cover-slip adapted to be placed on top thereof, means on the base engageable with the second cover-slip to hold it against movement when the block and the first cover-slip are moved longitudinally on the base, and means on the block for receiving and supporting the second cover-slip when the first cover-slip is moved from in under the same.

2. In an apparatus for preparing a film of blood between a pair of cover-slips, a base member, a block mounted on the base and longitudinally movable thereon, means on the block for receiving and securing one of the cover-slips, said second cover-slip adapted to be placed on top thereof, means on the base engageable with the second cover-slip to hold it against movement when the block and the first cover-slip are moved longitudinally on the base, and a pair of spaced raised supporting members on the block to receive the second cover-slip when the first-named coverslip is moved from in under the same.

3. In an apparatus for preparing a film of blood between a pair of cover-slips, a base member, said base having a groove formed therein and extending longitudinally of the base, a block mounted on the base and having a tongue extending into the groove, said block being movable longitudinally of the base and being guided by the tongue and groove, a pair of spring clamping arms on the block to receive and secure one of the coverslips, said second cover-slip adapted to be placed on top thereof, a pair of pins secured to the base, one on each side of the block and engageable with the second cover-slip to secure it against movement when longitudinal movement is imparted to the block and the first-named cover-slipsecured thereto, and a pair of spaced raised supporting members on the block to receive the second coverslip when the first-named cover slip is moved from in under the same.

4. In an apparatus for preparing a film of blood between a pair of cover-slips, a longitudinally movable member to receive and secure one of the cover-slips, said second cover-slip adapted to be placed on top thereof in a position where the adjacent surfaces of the cover-slips will be parallel and where blood placed on the first coverslip will be spread out into a film by the weight of the second cover-slip only, means for holding the second cover slip against movement whereby when movement is imparted to the movable member the first cover-slip will be pulled out from in under the second cover-slip in a plane parallel to the surface of the second cover slip, and equal films will be formed on the adjacent surfaces of the cover slips, and means for receiving and supporting the second cover-slip when the first-named cover-slip is pulled out, said means preventing smearing of the film formed on the second cover-slip.

DAVID J. B. LUBIN. 

